1. Field of the Invention
The invention relates generally to a method for producing hydrolysed keratinaceous material, such as feather meal or meal from hair.
2. Description of the Related Art
As a source of keratinaceous material, animal feathers, hair, hoof, nails and the like can be used. Feathers are by-products from poultry, and hair is a by-product from pigs, cattle, sheep and the like. Also hoofs or nails, that may be grinded, can be used as source of keratinaceous material. Such keratinaceous material has a high protein content, consisting of at least 17 amino acids. However, this keratinaceous material is hardly digestible for animals or humans because of the highly structured polypeptides, with the presence of many (di)sulphide bridges.
Many processes exist for producing (partly) hydrolysed keratinaceous material like feathers or hair, in order to increase the digestibility. Known methods include hydrolysis under pressure while using steam, enzymatic hydrolysis or chemical hydrolysis with e.g. base, acid or other reactive agent.
The keratinaceous material generally is not completely hydrolysed to mono-amino acids to improve the digestibility. In many processes, the resultant product from the partial hydrolysis of the keratinaceous material is partly insoluble in water, and may comprise a mixture of liquid (dissolved) and solid (insoluble) material. Generally, the combined product is converted to a dry solid material by a drying technique. The resultant product generally is not fully digestible for animals, according to for example the pepsin and/or ileal digestibility test. Further, it appears that such products can have anti-nutritional compounds, like lanthionine, in significant amounts.
Several examples of methods for producing partially hydrolysed keratinaceous material like feather meal include U.S. Pat. Nos. 5,772,968, 4,286,884 and 4,172,073. U.S. Pat. No. 4172073 is directed to the water soluble part of the hydrolysed feathers, and is therefore not relevant for the product that is only partially soluble.
Other references exist, that use in addition to steam, also chemical reactants that influence the chemical composition of the hydrolysed material, and cause more complicated work-up processes, as one has to handle the chemicals. Examples of these processes include WO2011/003015, that use oxidizing solutions at low pH, WO1990/01023 that additionally uses hydrogenperoxide, U.S. Pat. No. 4,232,123 that describes an acid hydrolysis followed with an enzymatioc hydrolysis, and EPO499260 that describes hydrolysis with sulphites.